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Questions in aged-care murder case: lawyer

The case against a former nurse accused of deliberately killing two aged-care residents with insulin in NSW does not add up, her trial has been told.

Megan Haines' barrister Troy Edwards said there was no proof the 49-year-old had administered the injections that killed Marie Darragh, 82, and Isobella Spencer, 77 at St Andrews Village at Ballina in May 2014.

The crown says Haines murdered the women after they and another resident, 88-year-old Marjorie Patterson, made complaints about her when she had already previously been suspended.

But Mr Edwards, giving his final submissions, said Haines only knew that Ms Darragh, Ms Patterson and a third unidentified resident had complained.

"You have no explanation, I suggest, as to why the accused did not kill Marjorie Patterson," he told the jury in Haines' Supreme Court trial on Tuesday.

The court has heard Ms Patterson was woken up and given Panadol by Haines the same night the other residents were allegedly given the lethal injections.

Insulin was later found missing from the wing's secure medication room.

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Mr Edwards said the amount of insulin missing wasn't enough to kill two people, and said no one saw Haines getting the insulin and there was no CCTV.

"I suggest to you, you would be far from satisfied that the accused was the only person with access to insulin," he said.

The court has heard Ms Spencer had complained that Haines had refused to help her to the toilet, while Ms Darragh had said the nurse refused to give her a cream to soothe an itch.

Crown prosecutor Brendan Campbell said Haines' nursing registration had been conditional following her previous suspension, and further complaints would potentially have been career ending.

He said the nurse had tried to "eliminate the cause" of the complaints ahead of a formal meeting about them, and had had a one-hour window that evening when she was the only nurse on night duty in the residents' wing.

"It is, in my submission, inconceivable that someone else could have murdered Ms Spencer and Ms Darragh," Mr Campbell said in his closing address on Tuesday.

Justice Peter Garling is due to begin summarising the evidence for the jury on Wednesday.